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MISR Ancillary Radiometric Product (ARP)
Processing Summary Page
Last update: July 10, 2001



The purpose of this page is to provide technical information, to the MISR science community, as to the status of the radiometric performance of the MISR cameras. An on-orbit experiment is conducted at bi-monthly intervals. At this time a diffuse panel reflects solar light into the cameras. The intensity of this light is measured with our on-board photodiodes, that is we utilize "detector-based" standards.With measured camera output DN and known incident radiances, we can compute radiometric calibration coefficients as a funtion of time in orbit. The coefficients are packaged into a file called the Ancillary Radiometric Product (ARP), and delivered to our data processing center, following each calibration. The information below tells you more about the algorithms used to produce these coefficients, how these algorithms have been changed over the mission life, and which file is currently being used in data processing. The site assumes the reader has an insiders view of the calibration experiment concept. More informaiton can be obtained from the calibration literature, or by contacting the MISR Calibration Scientist.

Ideally each investigator desires to have a data products derived from the best-available ARP coefficient file. To determine which ARP file was used to develop a given data product, you would use an HDF browser, such as HDF_Scan. (A unix-based procedure will also supply this information.) Read the metadata: annotation text that is part of the data file. Under Annotation Text: Input Data files, find the ARP version number used to produce your data, then compare it to the latest delivered ARP file that has been produced for that data acquisition date Active ARP section, below. If these files match, then you have most current version of the radiometric calibration file. If the files have not been constructed using the best-available, a crude adjustement of your data can be make by following the procedure below.

As of this date in time there are still some outstanding calibration issues to be resolved. The current ARP files for some of the time periods (T2-T5) have coefficients which cause the An Red-NIR bands to be 3% brighter than we believe is actually the case. Additionaly, the fore-aft camera radiances are biased by a few %. These errors are small, and will be corrected in new ARP files to be delivered later this summer. Until that time requesting that data products be re-processed is not recommended.

Calibration Experiment Timeline
(Orbit numbers and An times from IOT web page,

Orbit Time, UT Experiment
27-Feb-00 1043 23:34:24 Cal_North
28-Feb-00 00:33:53 Cal_South
00:49:04 Cal_Dark
01-Mar-00 1076 05:57:26 Cal_North
06:56:53 Cal_South
7:12:20 Cal_Dark
13-Mar-00 1259 19:31:21 Cal_North
1260 22:27:14 Cal_Dark
17-Mar-00 1314 14:09:48 Cal_North
15:27:05 Cal_Dark
1911 14:01:01 Cal_North
1912 16:39:15 Cal_South
17:01:02 Cal_Dark
2569 B40 18:50:07 Local Mode/ Lunar Lake
2575 04:16:43 Cal_North
2585 21:44:55 Cal_South
2586 ?? Data never found Cal_Dark
3717 14:24:46 Cal_North
3721 22:01:02 Cal_South
3721 22:21:13 Cal_Dark
4653 21:06:26 Cal_North
4654 18:29:27 Cal_South
4660 18:43:15 Cal_Dark
5351 19:29:18 Cal_North
5352 22:08:13 Cal_South
5353 22:36:11 Cal_Dark


6296 16:49:33 Cal_North
6297 19:28:53 Cal_South
6303 05:36:39 Cal_Dark
7169 15:27:58 Cal_North
7171 19:45:24 Cal_South
7177 05:59:52 Cal_Dark
8026 11:46:48 Cal_North
8028 16:04:05 Cal_South
8029 18:07:21 Cal_Dark

Algorithm basis


  MISR Calibration Publications listing
  In-flight Radiometric Calibration and Characterization (IFRCC) Algorithm Theoretical Basis Document, JPL D-13398, December 1999, Revision A. (Available electronically to the MISR Science Investigators.)

Algirithm change log:

First implementation Algorithm change
T001 (preflight) Laboratory calibration
T002_003 Mean G1 coefficient for each channel set to same as preflight channel mean. Pixel-to-pixel relative response determined from response to OBC diffuse panel. With this ARP vignetting of the Af and Aa cameras is removed, as well as a rippling (a small, ~1%, radiometric effect). This rippling may be due to slight changes within the camera filters. In this ARP release we also replaced the preflight quadratic calibration equation with a linear form,and constrained the DN versus radiance regression to report the dark current signal output for dark illumination conditions. With these changes two of the 3 calibration coefficients have been set to zero (G0=G2=0).
T002_0004 Use was made of the Blue HQE photodiode to establish the radiometic scale for all MISR channels.
T002_0005 Use was made of the June 11th Vicarious Calibration experiment to validate the Blue HQE photodiode. As a result of this study all radiances computed for MISR have been adjusted upwards by a factor of 1.10, irrespective of data acquisition time.
T008_0001 Beginning with this delivery, a quadratic calibration equation is being used to convert the sensor data from DN to radiances values. This algorithm may change the radiances reported over dark, or ocean targets, by a few percent. Radiances reported over bright scenes are believed to be invariant with algorithm. The calibration team has documented the basis and consequences of this change in several internal memorandum: [SDFM#241 - calibration equation study] [sdfm#247 - radiance change versus equation].
T009_0001 Separate calibration coefficients have been developed for the photodiodes as they view the North panel (used for aft and AN-red, nir channels) and the South panel (used for the fore- and AN-blue, green channels). This change is expected to improve fore-aft camera biases

Active ARPs

Time period name To be used for data acquired beginning: File name (1) First use in production
Date Time (UT) Orbit
T2 Feb 24, 2000 16:41:00 995 T002_F02_0005 February 15, 2001
Orbit 6169
T3 Jun 12, 2000 4:13:51 2575 T003_F02_0001
T4 Aug 29, 2000 14:18:37 3717 T004_F02_0001
T5 Nov 1, 2000 20:53:25 4653 T005_F02_0001
T6 Dec 19, 2000 19:13:59 5351 T006_F02_0001
T7 March 7, 2001 01:17:44 6476 T007_F02_0001 Same (2)
T8 May 17, 2001 01:19:09 7510 T008_F02_0001 Same (2)
T9 July 11, 2001 01:27:11 8311 T009_F02_0001 Same (2)

(1) SCF Directory: /data/bank/anc/ARP_INFLTCAL/database/MISR_AM1_ARP_INFLTCAL_*.hdf
(2) The date first used is the same as the time range start for usage of this file

Inactive ARPs

An inactive ARP is one that is no longer in use for MISR data product generation. These files have been superceded by the active files listed below.

Time period name File name (1) To be used for data acquired beginning: First used in production
T1 F01_001 Cover open March 2000
T2 T002_F01_003 Cover open July 15, 2000
T2 T002_F02_0004 Cover open August 24, 2000

(1) SCF Directory: /data/bank/anc/ARP_INFLTCAL/database/MISR_AM1_ARP_INFLTCAL_*.hdf

Channel mean coefficients
(for both active and inactive ARPs)


Gain coefficients (channel means)
Active files Inactive files Unreleased updates,
File construction date
Early Mission Degradation Report
T002_0005 T002_0003


T003_0001   T003_SCF0003
T004_0001   T4_SCF4

The 3/9/01 unreleased files would, if delivered to the DAAC, replace T002_0005, T003_0001, and T004_0001. They lower radiances in the An Red and NIR by about 3%. They will not be delivered to the DAAC, however, as several algorithm changes are planned before final production of these files.

Radiance calculations versus ARP

Linear model

A few investigators may wish to determine radiances that would have been computed if a specific ARP had been used in the L1B1 or L1B2 data production. As an example, say that a L1B2 data product was produced with ARP T002_0004, but it is now recommended that ARP T002_0005 be used for that data acquisition time period but the reprocessing has not yet occurred. This is a simplified case in that the G0 and G2 coefficients were set to zero for both these file.

We will define the ARP coefficients that were used in the data processing as G1_old coefficient, and the coefficients we wish had been used as G1_new. Since the MISR radiances are computed using

DN = G1_old * L_old
L_new = G1_old * L_old/ G1_new

One merely looks up the coefficients from the above tables to make the conversion. Note that there are some fine scale pixel-to-pixel corrections that will not be taken into account with this simplified algorithm. There are on the order of 1%. To make corrections to this level of accuracy, the data must be reprocessed.

In our example

G1_old(An_blue) = 22.5434
G1_new(An_blue) = 20.4269
L1_new=L1_old * 1.10

That is, there is a 10% increase in the radiance with the ARP update. This process will have to be repeated for each of the 36 channels.

Quadratic model

Beginning with ARP T8 a constrained quadratic has been used in our calibration equation. To convert the radiance values from one set of coefficients to another, a more generic equation is needed. The conversion for these files is:

DN = G0_old + G1_old * L_old + G2_old * L_old * L_old
L_new = -2[G0-DN]/{G1 + sqrt(G1*G1 - 4*G2*(G0-dn))}

The above equation is a variant to the usual quadratic inversion. It is preferred for instances where G2 is small.

Reference documents

Contact information